U.S. flood risk in the Anthropocene

Abstract A national depiction of high-resolution flood risk estimates has previously been thought to be beyond the grasp of reasonable computational capabilities. However, recent developments in inundation modelling now permit the first comprehensive national flood risk assessment of the US, which indicates an expected annual direct damage to property of 27 billion USD in 2020’s climate. Current flood risk is disproportionately borne by poorer and more White communities, and is concentrated on the Atlantic and Gulf coasts, the Northeast through Appalachia, and the Pacific Northwest. Under a medium-case concentration pathway (RCP4.5), we project a 37% increase in risk by 2050 due to climate change alone. This climate signal appears to disproportionately impact Black communities, with risk increases concentrated again on the Atlantic and Gulf coasts. Medium-case (SSP2) projections of population change cause flood risk increases that dwarf the impact of climate change by 4:1, illustrating the need for a holistic view on changes in risk with consideration of all its constituent causes. These results make clear the desperate need for adaptation to flood and emergent climate risks in the US, with mitigation required to prevent acceleration of this risk into the latter half of the century. These results can and should inform zoning, regulations, and targeted adaptation policies, as well as motivate wide reaching reforms in how flood risk and emergencies are managed.